[Frontend][Core] Revert "Add shutdown timeout" (#34730 and #36270) (#36628)

Signed-off-by: Mark McLoughlin <markmc@redhat.com>

vllm/v1/engine/coordinator.py

@@ -104,10 +104,8 @@ class DPCoordinator:
         """Returns tuple of ZMQ input address, output address."""
         return self.coord_in_address, self.coord_out_address
 
-    def shutdown(self, timeout: float | None = None) -> None:
-        """Shutdown coordinator process with configurable timeout."""
-        if self._finalizer.detach() is not None:
-            shutdown([self.proc], timeout=timeout)
+    def close(self):
+        self._finalizer()
 
 
 class EngineState: